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Method for preparing positive electrode material for secondary cell, and secondary cell

a technology of positive electrode material and secondary battery, which is applied in the direction of cell components, electrochemical generators, transportation and packaging, etc., can solve the problems of high production cost of cathode material, difficult control of cathode feed in a stoichiometric manner, and high cost of all secondary compounds. , to achieve the effect of high cathode performance, uniform and stable deposits of conductive carbon, and small diameter

Inactive Publication Date: 2009-02-17
KYUSHU UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a method for producing a cathode material for a secondary battery using a simple and practical technique. The method involves mixing a compound which releases phosphate ions in a solution with water and metal iron, adding lithium carbonate or hydroxide, and calcing the mixture. The resulting material has high surface conductivity and is firmly bonded together. The method can be carried out at a low cost and without the need for expensive or difficult-to-obtain ingredients. The resulting cathode material has improved performance in secondary batteries.

Problems solved by technology

However, the starting materials used in the above methods (1) to (3) are all secondary compounds which are expensive and difficult to obtain.
For example, Li3PO4 and iron oxalate (FeC2O4) are both relatively expensive and cause an increase in the production costs of the cathode material.
Fe3(PO4)2.8H2O as another iron compound can be synthesized from Na2HPO4 and Fe(II)SO4.7H2O, for example, but it is a hydrate whose hydration number is unstable and it is therefore difficult to control the feeding of it in a stoichiometric manner.
Also, since Fe3 (PO4)2.8H2O is obtained as a precipitate in the synthesis process thereof, a cumbersome process such as filtering is required to remove sodium ions and so on.
However, it is difficult to remove sodium ions and so on completely, and such a process may bring the entry of impurities.
As described above, the conventional techniques for producing LiFePO4 have problems of the entry of impurities and the necessity of a cumbersome process.
Also, since primary materials which are inexpensive and easily available such as metal iron cannot be used, the cost is unavoidably high.
Thus, any of the conventional techniques is not satisfactory as a method for producing LiFePO4 in an industrial scale.

Method used

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  • Method for preparing positive electrode material for secondary cell, and secondary cell
  • Method for preparing positive electrode material for secondary cell, and secondary cell
  • Method for preparing positive electrode material for secondary cell, and secondary cell

Examples

Experimental program
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Effect test

example 1

[0097](1) Preparation of Cathode Material:

[0098]A cathode material LiFePO4 was synthesized by the following procedure.

[0099]A mixture of 4.5 g of iron particles [under 325 mesh (44 μm) (purity 99.9%): product of The Nilaco Corporation] and 9.2901 g of 85% H3PO4 (product of Wako Pure Chemical Industries, Ltd.) was ground and reacted in an automatic grinding machine for two hours (when the viscosity of the mixture increased during grinding, distilled water was added to decrease the viscosity).

[0100]The reaction product was finely pulverized in a planetary ball mill for two hours. After addition of 3.381 g of LiOH.H2O, the mixture was further pulverized in the planetary ball mill for one hour. After removing water from the pulverized mixture with an evaporator, the mixture was vacuum-dried in a desiccator for two days. After addition of 0.6630 g of a coal pitch (product of Adchemco Corp., softening point: 250° C.), the mixture was manually ground for five minute to obtain a primary rea...

example 2

[0113](1) Preparation of Cathode Material:

[0114]A cathode material LiFePO4 was synthesized by the following procedure.

[0115]A mixture of 4.5 g of iron particles [under 325 mesh (44 μm) (purity 99.9%): product of The Nilaco Corporation] and 9.2901 g of 85% H3PO4 (product of Wako Pure Chemical Industries, Ltd.) was ground and reacted in an automatic grinding machine for two hours (when the viscosity of the mixture increased during grinding, distilled water was added to decrease the viscosity).

[0116]The reaction product (calcination precursor) was finely pulverized in a planetary ball mill for two hours. After addition of 3.381 g of LiOH.H2O, the mixture was further pulverized in a planetary ball mill for one hour. After removing water from the pulverized mixture with an evaporator, the mixture was vacuum-dried in a desiccator for two days.

[0117]The preliminary calcination was carried out in an atmosphere of nitrogen at 400° C. for five hours. After gas-cooled, the calcined product was...

example 3

[0128](1) Preparation of Cathode Material:

[0129]A cathode material LiFePO4 was synthesized by the following procedure.

[0130]A mixture of 1.5 g of iron powder [under 325 mesh (44 μm) (purity 99.9%): product of The Nilaco Corporation], 3.0967 g of 85% H3PO4 (product of Wako Pure Chemical Industries, Ltd.), and 1.1191 cc of hydrochloric acid (generally in the same number of moles as Li, Fe and PO4) was ground and reacted in an agate mortar for two hours. At this time, pure water was added as needed by dripping to decrease the viscosity of the mixture. After that, the mixture was placed in a beaker and ultrasonic wave was irradiated on the mixture for 40 minutes to accelerate the reaction. Then, the reaction mixture was pulverized in a planetary ball mill for two hours. After addition of 1.1270 g of lithium hydroxide, the mixture was further pulverized in the planetary ball mill for one hour. After removing water from the pulverized mixture with an evaporator, the mixture was dried in a...

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Abstract

A method for producing a cathode material for a secondary battery, characterized in that it comprises admixing a compound liberating a phosphate ion in a solution (phosphoric acid H3PO4, phosphorus pentoxide PO5, ammonium dihydrogenphosphate NH4H2PO4 and the like), water and metallic iron, adding lithium carbonate, lithium hydroxide or a hydrate thereof to the resultant mixture, and firing the resultant reaction product, to thereby synthesize LiFePO4.

Description

TECHNICAL FIELD[0001]The present invention relates to a method for producing a cathode material for a secondary battery and a secondary battery using the cathode material. More specifically, the present invention relates to a method for producing a cathode material LiFePO4 for a secondary battery using lithium or a compound thereof as an active material such as a metal lithium battery, lithium ion battery and lithium polymer battery, and to a secondary battery using the cathode material produced by the method.BACKGROUND ART[0002]LiFePO4 having an olivine-type (Pnma) crystal structure as a cathode material used in a secondary battery such as a metal lithium battery, lithium ion battery, or lithium polymer battery is subjected to electrode oxidation / reduction accompanied by doping / undoping of lithium during the process of charging and discharging. Such secondary batteries are attracting attention as large capacity batteries in recent years.[0003]Conventionally, the following methods h...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): H01M4/00C01B15/16H01M4/58C01B25/37C01B25/45H01M4/136H01M4/1397H01M10/052H01M10/0525H01M10/36
CPCC01B25/37H01M4/136H01M4/1397H01M4/5825H01M10/052H01M10/0525H01M4/0471Y02E60/122Y02T10/7011Y02E60/10H01M4/58C01B25/45Y02T10/70
Inventor OKADAYAMAKIHATTA, NAOKIUCHIYAMA, IZUMIINABA, TOSHIKAZU
Owner KYUSHU UNIV
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